Same Flue for Oil and Coal Boilers???

Hello everyone,
I just found this site, its great. I haven't found a answer to this question. Can you use the same flue for the oil and coal boilers or should they always have their own. My plan was to install a coal boiler to the same flue, but a contractor just told me that you never do that. Is he correct????

Your contractor is correct, it is against building code. That said, my house has had a radiant stove and oil boiler hooked into the same chimney for 30+ years. If you have the option, you may want to power vent the oil boiler and run the coal boiler into the chimney.

It's also most likley that once you have the coal boiler hooked up, you won't need to use the oil burner. They certainly should not fire at the same time.

Forgetting for a moment that it's against code, why couldn't the oil and the coal boilers be on the same flue and fire at the same time? The baro for my oil burner is set for very low draft, much less draft than the chimney can produce, and it could handle a considerably bigger oil burner than is actually installed. So what's the difference between running coal and oil together into one flue, or running an oil burner twice as big? I think when I was on the Field Controls web site looking at diagrams on how to mount the baro, they had examples of how to combine several appliances into one flue, and where to mount the individual baros for the individual burners. Or did I dream that .... I'm never sure anymore....

It's just big brother protecting us from ourselves. Yes, it's against code, I'll assume everywhere now. Yes, it has been done without issue. I always thought it stemmed from a wood stove and some other appliance in the same flu. If there's a chimney fire with just a wood stove, you shut down the air & the fire goes out. If there's a boiler in the same flu, the damper allows air to feed the fire.

rberq wrote: I think when I was on the Field Controls web site looking at diagrams on how to mount the baro, they had examples of how to combine several appliances into one flue, and where to mount the individual baros for the individual burners. Or did I dream that .... I'm never sure anymore....

The examples are for like appliances.

coalkirk wrote: They certainly should not fire at the same time.

Not true, they can operate together or independantly if done right. Anyone that wants to do this can PM me for Burnam Boiler's recommendations in the proper installation. I don't advise it as it is against code, but the code is wrong when it comes to coal. I think the concern is that a lot of coal appliances will also see wood burned in them at some point.

So it seems as though it's actually OK but against code. But generally, you should not try to run both at the same time. Thank you for all the responses

biggreen1 wrote:you should not try to run both at the same time.

Except at startup, the need for running both would be a highly unlikely event anyway unless the solid fuel appliance was undersized for the load or the domestic water is off the oil burner.

It is against code but it can be done. I know someone who did it.
I don't recommend doing anything that is against building codes.

I just talked to a chimney guy on long Island,NY and he said you can have 2 devices like coal stove and oil burner in the same chimney but the chimney flu must be 7" and the 2 devices are 6" each. he said you cannot share a chimney with a wood burning device.
If you want to connect a oil burner and a coal boiler in the same chimney.
the Harman VF3000 coal boiler has a 6" chimney pipe.
the keystoker KAA-2 coal boiler has a 6" chimney pipe.
the AHS-S130 coal boiler has a 5" chimney pipe.

of course check your local codes before doing this.

syncmaster wrote:I just talked to a chimney guy on long Island,NY and he said you can have 2 devices like coal stove and oil burner in the same chimney but the chimney flu must be 7" and the 2 devices are 6" each. he said you cannot share a chimney with a wood burning device.
If you want to connect a oil burner and a coal boiler in the same chimney.
the Harman VF3000 coal boiler has a 6" chimney pipe.

Your saying they must share a common thimble? This is what Burnham Boiler recommends, the two are connected by stovepipe prior to the chimney.

coaledsweat wrote:[

Your saying they must share a common thimble? This is what Burnham Boiler recommends, the two are connected by stovepipe prior to the chimney.

Yes, that is right the two 6" heating devices can share the 7" chimney through a common thimble.

If sharing a chimney is not allowed where you live another alternitive if your oil boiler chimney has a 7" flu.
You can replace you oil boiler with a Harman vf3000 with a optional oil burner.
to change from burnning coal to oil you must remove a cover that covers the oil nozzle and flick a switch from coal to oil.
the price for the VF3000 is as follows:
vf3000 boiler with hopper and stoker $4200.00
oil burner option $750.00
DHW coil $250.00
total $5200.00 plus shipping and tax

Reading all your input has been a great learning exp for me. While we are on the subject is there any problem with having two coal fired units with 6" flues connected to the same 8" SS chimney?